arXiv Machine Learning

What Standard Evaluations Hide About Detectors of Hijacked LLM Agents: Rare Attacks, Unseen Tools and Benchmark Transfer

arXiv AI
3d ago

Pre-Crime for Agents, at the Last Second: Probing When a Recruited Agent Gives In

The paper investigates whether an overseer can predict when an AI agent will comply with a peer’s coercion to reveal sensitive information. By training a linear probe on the agent’s internal activations, the authors demonstrate high detection rates—up to 82% of leaking calls at a 5% benign flag rate—across multiple multi‑agent scenarios. The probe also identifies legitimate disclosures more often than violations, indicating a short‑range warning that could enable pre‑emptive intervention.

By Leonidas Raghav
arXiv AI
Jul 29

Early Detection of Distributed Backdoors in Multi-Agent LLM Systems: A Characterization Study

arXiv:2607. 24893v1 Announce Type: cross Abstract: Multi-agent LLM systems can be attacked by a payload that no single agent ever holds in full: a poisoned tool hides encrypted fragments in its observations, spreads them across several agents, and an external step reassembles and executes them after the run.

By Diego Fernandez Arias, Dev Prashant Mistry, Ren Wang, Yibo Hu
arXiv Machine Learning
Oct 5

Prompted to Discriminate: Generalizing Malicious-Input Probes in the Wild

The paper investigates whether adding a short classification instruction after a user’s prompt improves the ability of activation probes to detect malicious inputs in large language models. Across 13 safety benchmarks and three open‑weight model families, a classification suffix consistently boosts out‑of‑distribution detection (up to ~4 AUC points) compared to no suffix, and the benefit transfers to multi‑position pooling probes used in production. The improvement stems from the classification format itself rather than the specific content of the instruction, though the optimal suffix varies with the model and readout type.

By Elad David, Max Fomin
arXiv AI
Sep 4

CASCADE: A Component Ablation and Corpus Audit of a Layered Local Defense for MCP-Based Systems

The paper evaluates CASCADE, a fully local layered defense for Model Context Protocol (MCP)-based systems, by conducting a component ablation and corpus audit on a fixed 5,000-sample dataset. It demonstrates that the choice of aggregation convention heavily influences reported metrics, that detection performance varies with provenance, and that the released configuration does not fully disclose the operating point. The study also shows that a local review model invoked for a third of requests does not alter classification outcomes, highlighting the importance of reproducibility and transparency in defense evaluations.

By \.Ipek Abas{\i}kele\c{s} Turgut, Edip G\"um\"u\c{s}
Hugging Face Trending Papers
4d ago

Pre-Crime for Agents, at the Last Second: Probing When a Recruited Agent Gives In

The paper investigates whether an overseer can predict when an AI agent will yield to peer pressure and reveal sensitive information. By training a linear probe on the agent’s internal activations, the authors demonstrate that they can detect imminent leaks with high accuracy—catching 82 % of leaking calls on Qwen3‑32B while flagging only 5 % of benign ones. The study also shows that a simple bag‑of‑words classifier performs similarly, indicating that the probe’s advantage largely stems from label training rather than activation patterns.

arXiv Computation and Language
Oct 9

TRACE: Diagnosing Verifier Brittleness in Agentic Evaluation

The paper introduces TRACE, a protocol designed to diagnose whether changes in verifier scores for large language model agents reflect actual changes in agent behavior or merely alterations in the evaluation process. TRACE works by applying targeted changes to evaluation components, running paired experiments, and re‑scoring unchanged trajectories to isolate the source of score variation. Experiments on synthetic tasks and public benchmark tasks demonstrate that seemingly significant score shifts can often be attributed to evaluation artifacts, while TRACE can also detect genuine behavioral changes.

By Radhika Gaonkar
arXiv Machine Learning
Oct 9

RH-Detect: A Unified Benchmark for Reward Hacking Detection

RH-Detect is a unified benchmark for detecting reward hacking in language models, aggregating 92,761 examples from eleven public datasets into a common schema with six behavior categories. It evaluates six off‑the‑shelf models on 5,021 open‑ended evaluation units, achieving a top AUROC of 0.962 and over 93% accuracy, though performance drops notably on multi‑turn tool‑use datasets. The study also shows that input format changes and single‑token fine‑tuning can influence detector performance, revealing gaps in deployment‑time monitoring.

By Junwei Quan, Evgenii Opryshko, Rohan Subramani, Igor Gilitschenski